This invention relates to the analytical arts and to recombinant DNA technology. In particular the invention pertains to the construction and purification of novel strains of yeast and other fungi that are useful in whole-cell screens for inhibitors of inositolphosphoryl ceramide synthase (IPC Synthase).
The incidence of life-threatening fungal infections is increasing at an alarming rate. With the exception of Staphylococci infections, the fungus C. albicans represents the fastest growing area of concern in hospital acquired infections. About 90% of nosocomial fungal infections are caused by species of Candida with the remaining 10% being attributable to Aspergillus, Cryptococcus, and Pneumocystis. While effective antifungal compounds have been developed for Candida there is growing concern that the rise in fungal infections may portend a trend toward escalating resistance and virulence in the future. This is problematic because anti-Candida compounds rarely possess clinically significant activity against other fungal species.
Inositolphosphoryl ceramides are sphingolipids found in a number of fungi including but not limited to S. cerevisiae, S. pombe, C. albicans, A. fumigatus, and H. capsulatum. A step of sphingolipid biosynthesis that is unique to fungi and plants is catalyzed by the enzyme IPC synthase. The IPC synthase step, which covalently links inositol phosphate and ceramide, is essential for viability in S. cerevisiae. Although some elements of sphingolipid biosynthesis in fungi are shared with mammalian systems, the pathways diverge after formation of ceramide. Thus, the formation of inositolphosphoryl ceramide is unique to fungi and plants, making IPC synthase a good molecular target for antifungal chemotherapy.
While IPC synthase presents a rational target for anti-fungal therapy, presently there are no clinically useful compounds that act at this step. Thus, there is a need for new compounds that inhibit IPC synthase.